Numerous constructions of slot milling tools are known. In one known case, the holding of the inserts is entrusted the inherent elasticity of the disc material wherein a self locking effect is achieved by displacing a portion of material adjacent the seat out of its rest position and by elastical force holds the insert in its inserted position. The force biassing the insert corresponds to the force necessary to displace the material portion so much as allowing the insert to be inserted.
On devices arranged according to the known art, there always is a risk for fatigue or diminishing of the elasticity or the spring power of the material portion displaced resulting in a reduction or loss of the intended holding force. This implies especially at high speed rotating milling discs not only a technical disadvantage but also a great risk for personal injuries in that disengaging inserts with high power like bullets can be thrown long distances.